What Does A Substance’S RF Value Depend On?

What factors determine the RF value of pigments?

The Rf value of each pigment was determined by dividing its migration by the migration of the solvent.

It was determined that 4 pigments were present in the original spot — carotene, xanthophyll, chlorophyll a, and chlorophyll b.

Xanthophyll Carotene was the most soluble, while chlorophyll b was the least soluble..

Why is the RF value less than 1?

Rf values are alwaysless than 1. An Rf value of 1 or too close to it means that the spot and the solvent front travel close together and is therefore unreliable. This happens when the eluting solvent is too polar for the sample.

Which pigment has the highest RF value?

LuteinPigmentRf value rangeRelative positionLutein0.22-0.28Below, or almost at the same level of, the highest greenViolaxanthin0.13-0.19Below, or almost at the same level of, the highest greenNeoxanthin0.04-0.09Below, or almost at the same level of, the highest green

Why does carotene have a high RF value?

The Rf value of the xanthophyll is two thirds that of carotene because xanthophyll has an H bond with cellulose, which slows it down, and makes it less soluble in the solvent. Carotene is more soluble in 9:1 petroleum-ether acetone solution, which caused it to be carried higher and have a larger Rf value.

On what factors Rf value depends?

Retention Factor Rf values and reproducibility can be affected by a number of different factors such as layer thickness, moisture on the TLC plate, vessel saturation, temperature, depth of mobile phase, nature of the TLC plate, sample size, and solvent parameters. These effects normally cause an increase in Rf values.

Why is RF useful?

R f values can be used to identify unknown chemicals if they can be compared to a range of reference substances. The Rf value for a particular substance is always the same if the same solvent and stationary phase are used.

Can Rf value be greater than 1?

Long Answer: Rf is the “Retardation Factor”, which is the ratio of the distance traveled by a compound in a mobile phase compared with the distance traveled by the front of the mobile phase itself. It is always greater than or equal to zero, and less than or equal to 1.

Why silica gel is used in TLC?

Silica gel is by far the most widely used adsorbent and remains the dominant stationary phase for TLC. … The surface of silica gel with the highest concentration of geminal and associated silanols is favored most for the chromatography of basic compounds because these silanols are less acidic.

How would the RF values change if a more polar solvent were used?

In general, how will Rf values change with increasing solvent polarity? Rf values increase with increasing solvent polarity as substance are more attracted to the solvent and therefore move with it.

What happens to RF values when you change solvents?

As, mentioned by Jan Increasing the polarity of solvent will result in increase in Rf value as the compound in even for polar or nonpolar compound, this is the rule of thumb in most cases, may be except do exist i don’t know about it. But for my experience in the laboratory polarity result increase in Rf value.

What determines RF value?

The Rf value of a compound is equal to the distance traveled by the compound divided by the distance traveled by the solvent front (both measured from the origin).

How do you reduce RF values?

If you want the Rf of your TLC spot to be smaller, i.e., the spot to be lower down on the plate, you must decrease the eluent polarity. Either choose a different eluent (solvent) or adjust the solvent ratio by increasing the percentage of the nonpolar solvent relative to the polar solvent in the eluent.

What does a high RF value mean?

A high Rf (Ie 0.92) would refer to a substance that is very non-polar. Ie that substance moved a 92% of the entire distance the solvent traveled. A low Rf value (0.10) would refer to a substance that is very polar. IE that substance was only able to move 10% of the entire distance the solvent traveled. Term.

How do you increase Rf value?

The stronger a compound is bound to the adsorbent , the slower it moves up the TLC plate. Non-polar compounds move up the plate most rapidly (higher Rf value), whereas polar substances travel up the TLC plate slowly or not at all (lower Rf value).

Why is RF value important?

This allows unknowns to be compared to known materials. If the retention factor of an unknown does not match that of a known material, they are not the same compound. … Interactions of the individual components with each other and the concentration of the component in the sample will both affect the Rf value.

What does it mean if the RF value is 0?

did not moveThe distance a particular molecule, or spot, travels relative to the distance travelled by the eluting solvent is called the Rf value. The Rf value ranges from 0 (indicating the molecule did not move up the plate at all) to 1 (indicating the molecule traveled all the way up the plate).

Why RF values are different?

The larger an Rf of a compound, the larger the distance it travels on the TLC plate. When comparing two different compounds run under identical chromatography conditions, the compound with the larger Rf is less polar because it interacts less strongly with the polar adsorbent on the TLC plate.

What is the RF value for Xanthophyll?

0.15-0.35Therefore, pigments 1 and 2 are likely to be carotenes, and pigment 4 is likely to be a xanthophyll. Pigment 3 is likely to be chlorophyll, since it is more polar than carotenes but less polar than xanthophylls….Explanation.PigmentRf valueXanthophylls0.15-0.354 more rows•Jun 21, 2019